The present invention relates generally to underwater welding, and, more specifically, to underwater laser welding.
Underwater welding techniques are used in building and repair of off-shore oil rigs, ships, nuclear reactors, and other similar applications. In many cases, a manual arc welding procedure is used, meaning that an individual is performing the underwater welding operation. Manual underwater welding is often required when there is limited access to the welding region.
There are also many cases where underwater welding is effected by remote robotic control. Operator safety is greatly enhanced when robotically controlled underwater welding is used. This is especially true for welding operators when addressing certain repair procedures within the nuclear industry. This is also true when addressing potential mitigation issues in the irradiated region of a nuclear reactor. Such mitigation issues include the concerns of stress corrosion cracking (SSC) of nuclear reactor components in both the irradiated and non-irradiated regions of the reactor.
Many arc related techniques are adaptable to performing surfacing, joining, and removal operations underwater. For welding or cladding underwater, the following are a few among many that have proven to be effective: plasma transferred arc (PTA), gas tungsten metal arc (GTMA), and tungsten inert gas (TIG).
Laser welding or cladding is also an approach. In particular, laser surface cladding is a process in which powder or wire of different compositions is delivered into the laser-generated melt pool, and the powder or wire is also melted by the laser beam. A thin or thick layer of clad alloy is formed having a chemistry that is different from the substrate.
The main purpose of the laser cladding process is to overlay the surface of a substrate with another material having a different chemistry by melting a thin or thick interfacial layer to produce a metallurgical bond with minimum dilution of the clad layer. Among the advantages of this technique are production of novel alloys, minimized clad dilution, reduced alloy material loss, reduced machining, and reduced distortion.
Conventional laser welding occurs in a gas environment, typically using a suitable inert cover gas. Therefore, conventional laser welding will not work underwater because the water environment affects the laser beam and cover gas, and rapidly removes heat from the work zone. Accordingly, an apparatus specifically configured to allow underwater welding with a laser beam is desired for enjoying the benefits associated with such welding.